Say i have 2 tables, person and job.
+--------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| name | varchar(255) | NO | | NULL | |
| job_id | int(11) | NO | | NULL | |
+--------+--------------+------+-----+---------+----------------+
+----------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+----------+--------------+------+-----+---------+----------------+
| j_id | int(11) | NO | PRI | NULL | auto_increment |
| j_name | varchar(255) | NO | | NULL | |
| j_active | tinyint(1) | NO | | 0 | |
+----------+--------------+------+-----+---------+----------------+
How would i do a select where it only returns a job_id where j_active = 1 and otherwise return 0 or NULL? So, I would want to always return all persons but when their job isn't active i dont want to return their job id
select * from person p left join job j on p.job_id=j.j_id and j.j_active=1
A case statement should work. Something like:
select name, case when j_active=1 then job_id else null end as job_id
from person join job on (person.job_id=job.j_id)
Related
Two table are populated from a CSV file :
routers:
+------------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| type_id | int(11) | YES | MUL | NULL | |
| identificationID | varchar(255) | NO | | NULL | |
| wep | varchar(255) | NO | | NULL | |
| ssid | varchar(255) | NO | UNI | NULL | |
+------------------+--------------+------+-----+---------+----------------+
and
pickups:
+--------------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| type_id | int(11) | YES | MUL | NULL | |
| enable | tinyint(1) | YES | | NULL | |
| name | varchar(255) | NO | | NULL | |
| adress | varchar(255) | YES | | NULL | |
| zip | varchar(255) | YES | | NULL | |
| city | varchar(255) | YES | | NULL | |
| googleGeoCode | varchar(255) | YES | | NULL | |
| agent | tinyint(1) | YES | | NULL | |
| userRestricted | tinyint(1) | YES | | NULL | |
| superUserPickup_id | int(11) | YES | UNI | NULL | |
| telephone | varchar(255) | YES | | NULL | |
+--------------------+--------------+------+-----+---------+----------------+
Because everything comes from Excel, I need a SQL code to populate a third table which is
pickup_has_router :
+-----------+----------+------+-----+-------------------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-----------+----------+------+-----+-------------------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
| router_id | int(11) | YES | MUL | NULL | |
| pickup_id | int(11) | YES | MUL | NULL | |
| timeStamp | datetime | NO | | CURRENT_TIMESTAMP | |
+-----------+----------+------+-----+-------------------+----------------+
For example, I know that below routers have the pickup ID n°1, and I know how to fetch them
SELECT * FROM `routers` WHERE `identificationID` IN(
'UCDDU17805001464',
'UCDDU17805001029',
'UCDDU17805000137',
'UCDDU17805000129',
'UCDDU17805001394'
)
But from the result of above statment, how to loop the INSERT statment which would be something like:
INSERT INTO `pickup_has_router` (`id`, `router_id`, `pickup_id`, `timeStamp`)
WHERE `identificationID` IN(
'UCDDU17805001464',
'UCDDU17805001029',
'UCDDU17805000137',
'UCDDU17805000129',
'UCDDU17805001394'
)
VALUES (NULL, 'router.id', '1', CURRENT_TIMESTAMP);
Thanks for the help.. I have been searching quite a lot and yes SQL is not my best skill :-))))))
insert into `pickup_has_router` (`router_id`, `pickup_id`)
select `id`, 1 from `routers`
where `identificationID` in(
'UCDDU17805001464',
'UCDDU17805001029',
'UCDDU17805000137',
'UCDDU17805000129',
'UCDDU17805001394'
)
When doing an insert, instead of the values clause you can use a select statement, where the columns returned by the select statement match the columns required by the insert.
Below is schema description. I would like to construct a query that for a given user will return all the cases that are shared directly via case_users OR indirectly via case_groups table. Here is my attempt, where I pull the groups the user belongs to upfront:
SELECT * FROM `cases`
INNER JOIN `case_users` ON `cases`.`id` = `case_users`.`case_id`
INNER JOIN `case_groups` ON `cases`.`id` = `case_groups`.`case_id`
WHERE `case_users`.`user_id` = '<USER_ID>'
OR `case_groups`.`group_id` IN (<USER_GROUP_LIST>)
EXPLAIN returns the following: Impossible WHERE noticed after reading const table...
How can I get it done? Ideally I would like to retrieve all the cases in a single shot - without pulling the USER_GROUP_LIST - groups that the user belongs to.
mysql> describe users;
+-------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
+-------------+--------------+------+-----+---------+----------------+
mysql> describe cases;
+-------------+--------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+-------------+--------------+------+-----+---------+----------------+
| id | int(11) | NO | PRI | NULL | auto_increment |
+-------------+--------------+------+-----+---------+----------------+
mysql> describe case_users;
+-------------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------+---------+------+-----+---------+-------+
| user_id | int(11) | NO | PRI | NULL | |
| case_id | int(11) | NO | PRI | NULL | |
+-------------+---------+------+-----+---------+-------+
mysql> describe case_groups;
+-------------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------+---------+------+-----+---------+-------+
| case_id | int(11) | NO | PRI | NULL | |
| group_id | int(11) | NO | PRI | NULL | |
+-------------+---------+------+-----+---------+-------+
mysql> describe group_users;
+-------------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------------+---------+------+-----+---------+-------+
| group_id | int(11) | NO | PRI | NULL | |
| user_id | int(11) | NO | PRI | NULL | |
+-------------+---------+------+-----+---------+-------+
Your joins will only return cases whose Id is in both the case_users and case_groups..
If its one or the other, then you need 2 queries, which you can UNION to get all the results in a single resultset:
SELECT `cases`.* FROM `cases`
INNER JOIN `case_users` ON `cases`.`id` = `case_users`.`case_id`
WHERE `case_users`.`user_id` = '<USER_ID>'
UNION
SELECT `cases`.* FROM `cases`
INNER JOIN `case_groups` ON `cases`.`id` = `case_groups`.`case_id`
WHERE `case_groups`.`group_id` IN (SELECT `group_users`.`group_id`
FROM `group_users`
WHERE `group_users`.`user_id` = '<USER_ID>')
Why am I getting ERROR 1222 (21000): The used SELECT statements have a different number of columns from the following?
SELECT * FROM friends
LEFT JOIN users AS u1 ON users.uid = friends.fid1
LEFT JOIN users AS u2 ON users.uid = friends.fid2
WHERE (friends.fid1 = 1) AND (friends.fid2 > 1)
UNION SELECT fid2 FROM friends
WHERE (friends.fid2 = 1) AND (friends.fid1 < 1)
ORDER BY RAND()
LIMIT 6;
users:
+------------+---------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------+---------------+------+-----+---------+----------------+
| uid | int(11) | NO | PRI | NULL | auto_increment |
| first_name | varchar(50) | NO | | NULL | |
| last_name | varchar(50) | NO | | NULL | |
| email | varchar(128) | NO | UNI | NULL | |
| mid | varchar(40) | NO | | NULL | |
| active | enum('N','Y') | NO | | NULL | |
| password | varchar(64) | NO | | NULL | |
| sex | enum('M','F') | YES | | NULL | |
| created | datetime | YES | | NULL | |
| last_login | datetime | YES | | NULL | |
| pro | enum('N','Y') | NO | | NULL | |
+------------+---------------+------+-----+---------+----------------+
friends:
+---------------+--------------------------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+---------------+--------------------------------------+------+-----+---------+----------------+
| friendship_id | int(11) | NO | MUL | NULL | auto_increment |
| fid1 | int(11) | NO | PRI | NULL | |
| fid2 | int(11) | NO | PRI | NULL | |
| status | enum('pending','accepted','ignored') | NO | | NULL | |
+---------------+--------------------------------------+------+-----+---------+----------------+
UNIONs (UNION and UNION ALL) require that all the queries being UNION'd have:
The same number of columns in the SELECT clause
The column data type has to match at each position
Your query has:
SELECT f.*, u1.*, u2.* ...
UNION
SELECT fid2 FROM friends
The easiest re-write I have is:
SELECT f.*, u.*
FROM FRIENDS AS f
JOIN USERS AS u ON u.uid = f.fid2
WHERE f.fid1 = 1
AND f.fid2 > 1
UNION
SELECT f.*, u.*
FROM FRIENDS AS f
JOIN USERS AS u ON u.uid = f.fid1
WHERE f.fid2 = 1
AND f.fid1 < 1
ORDER BY RAND()
LIMIT 6;
You've LEFT JOIN'd to the USERS table twice, but don't appear to be using the information.
In the following example, MySQL fails to use to find a ref for the JOIN clause (or so it appears). Can anyone explain why?
mysql> explain SELECT 1
FROM `businesses`
INNER JOIN `categories`
ON (`businesses`.`id` = `categories`.`business_id`)
WHERE (`categories`.`category_id` IN (1321, 7304, 9189, 4736, 4737, 1322, 8554, 1323, 1324, 9459, 1325, 1326, 4738, 1327, 1328, 1329, 1330, 1331, 1332, 1333, 1334, 8031, 8387)
AND `businesses`.`id` <= 170261
AND `businesses`.`id` >= 160262 ) ;
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra
+----+-------------+-------------------------------------+-------+--------------------------+-------------+---------+------+-------+-
| 1 | SIMPLE | businesses | range | PRIMARY | PRIMARY | 4 | NULL | 20492 | Using where
| 1 | SIMPLE | categories | range | business_id,idx_category | business_id | 10 | NULL | 20584 | Using where; Using index
+----+-------------+-------------------------------------+-------+--------------------------+-------------+---------+------+-------+-
categories table:
| categories | CREATE TABLE `categories` (
`id` int(11) NOT NULL auto_increment,
`business_id` int(10) unsigned default NULL,
`category_id` int(10) unsigned default NULL,
`country_id` char(2) default NULL,
`state_id` int(10) unsigned default NULL,
`city_id` int(10) unsigned default NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `business_id` (`business_id`,`category_id`),
KEY `idx_category2` (`country_id`,`state_id`,`city_id`,`category_id`),
KEY `idx_category` (`category_id`)
) ENGINE=InnoDB AUTO_INCREMENT=13155275 DEFAULT CHARSET=latin1 |
Index info on categories:
+-------------------------------------+------------+---------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment |
+-------------------------------------+------------+---------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
| categories | 0 | PRIMARY | 1 | id | A | 13154781 | NULL | NULL | | BTREE | |
| categories | 0 | business_id | 1 | business_id | A | 13154781 | NULL | NULL | YES | BTREE | |
| categories | 0 | business_id | 2 | category_id | A | 13154781 | NULL | NULL | YES | BTREE | |
| categories | 1 | idx_category2 | 1 | country_id | A | 17 | NULL | NULL | YES | BTREE | |
| categories | 1 | idx_category2 | 2 | state_id | A | 17 | NULL | NULL | YES | BTREE | |
| categories | 1 | idx_category2 | 3 | city_id | A | 53913 | NULL | NULL | YES | BTREE | |
| categories | 1 | idx_category2 | 4 | category_id | A | 13154781 | NULL | NULL | YES | BTREE | |
| categories | 1 | idx_category | 1 | category_id | A | 51995 | NULL | NULL | YES | BTREE | |
+-------------------------------------+------------+---------------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+
Maybe it's because you're not looking for all categories with that business_id, but further limit the categories like;
WHERE (`categories`.`category_id` IN (1321, 7304, 9189, etc)
The MySQL guide has an article on the range join type that might be relevant.
I have a table that uses 3 foreign keys into other tables. When I perform a left join, I get duplicate columns. MySQL says that the USING syntax will reduce the duplicate columns, but there aren't examples for multiple keys.
Given:
mysql> describe recipes;
+------------------+------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------------+------------------+------+-----+---------+-------+
| ID_Recipe | int(11) | NO | PRI | NULL | |
| Recipe_Title | char(64) | NO | | NULL | |
| Difficulty | int(10) unsigned | NO | | NULL | |
| Elegance | int(10) unsigned | NO | | NULL | |
| Quality | int(10) unsigned | NO | | NULL | |
| Kitchen_Hours | int(10) unsigned | NO | | NULL | |
| Kitchen_Minutes | int(10) unsigned | NO | | NULL | |
| Total_Hours | int(10) unsigned | NO | | NULL | |
| Total_Minutes | int(10) unsigned | NO | | NULL | |
| Serving_Quantity | int(10) unsigned | NO | | NULL | |
| Description | varchar(128) | NO | | NULL | |
| ID_Prep_Text | int(11) | YES | | NULL | |
| ID_Picture | int(11) | YES | | NULL | |
| Category | int(10) unsigned | NO | | NULL | |
| ID_Reference | int(11) | YES | | NULL | |
+------------------+------------------+------+-----+---------+-------+
15 rows in set (0.06 sec)
mysql> describe recipe_prep_texts;
+------------------+---------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------------+---------------+------+-----+---------+-------+
| ID_Prep_Text | int(11) | NO | PRI | NULL | |
| Preparation_Text | varchar(2048) | NO | | NULL | |
+------------------+---------------+------+-----+---------+-------+
2 rows in set (0.02 sec)
mysql> describe recipe_prep_texts;
+------------------+---------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+------------------+---------------+------+-----+---------+-------+
| ID_Prep_Text | int(11) | NO | PRI | NULL | |
| Preparation_Text | varchar(2048) | NO | | NULL | |
+------------------+---------------+------+-----+---------+-------+
2 rows in set (0.02 sec)
mysql> describe mp_references;
+--------------+---------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+--------------+---------+------+-----+---------+-------+
| ID_Reference | int(11) | NO | PRI | NULL | |
| ID_Title | int(11) | YES | | NULL | |
| ID_Category | int(11) | YES | | NULL | |
+--------------+---------+------+-----+---------+-------+
3 rows in set (0.00 sec)
My query statement:
SELECT *
FROM Recipes
LEFT JOIN (Recipe_Prep_Texts, Recipe_Pictures, mp_References)
ON (
Recipe_Prep_Texts.ID_Prep_Text = Recipes.ID_Prep_Text AND
Recipe_Pictures.ID_Picture = Recipes.ID_Picture AND
mp_References.ID_Reference = Recipes.ID_Reference
);
My objective is to get one row of all the columns from the join without duplicate columns. I'm using MySQL C++ Connector to send the SQL statements and retrieve result sets. I believe that the C++ Connector is having issues with duplicate column names.
So what is the SQL statement syntax that I should use?
Reference to MySQL JOIN syntax
I believe the following should work:
SELECT *
FROM Recipes
LEFT JOIN Recipe_Prep_Texts USING (ID_Prep_Text)
LEFT JOIN Recipe_Pictures USING (ID_Picture)
LEFT JOIN mp_References USING (ID_Reference)
Since it looks like most of the tables you are joining on have a few columns except for the first one, how about:
SELECT Recipes.*,
Recipe_Prep_Texts.Preparation_Text,
Recipe_Pictures.Foo, -- describe is missing in OP
mp_References.ID_Title,
mp_References.ID_Category
FROM Recipes
LEFT JOIN (Recipe_Prep_Texts, Recipe_Pictures, mp_References)
ON (
Recipe_Prep_Texts.ID_Prep_Text = Recipes.ID_Prep_Text AND
Recipe_Pictures.ID_Picture = Recipes.ID_Picture AND
mp_References.ID_Reference = Recipes.ID_Reference
);
I can't tell you how many times I wished I had
SELECT (* - foo) FROM table
especially in cases where foo is some huge field like a BLOB and I just want to see everything else without breaking the formatting.
You are selecting * from the combined resulting table. Limit that * to whatever columns you want to keep.
Try the following query:
SELECT name,ac,relation_name
FROM table1
LEFT JOIN table2 USING (ID_Prep_Text)
LEFT JOIN table3 USING (ID_Picture);